In many chemical processes small quantities of gaseous HCl are generated as an impurity. For example, in the production of high octane fuels by catalytic reforming of low octane gasoline fractions, a chlorine-promoted catalyst, generally platinum, is employed and during the reforming operation a portion of the chlorine content is converted to HCl. The reforming operation also generates hydrogen which is usually recycled to the reforming reactor and if this recycled portion, containing the HCl impurity even in small amounts, is recycled it can seriously interfere with the operation and also cause corrosion upon contact with the moisture content of the gas. In other vapor-phase chemical operations, where a metal chloride, such as AlCl.sub.3 or FeCl.sub.3, is used as a catalyst, the formation of HCl as an impurity becomes possible and removal of this impurity is required in order to avoid corrosion of the process equipment or environmental problems resulting from the release of the HCl-containing gas to the atmosphere.
In the past active alumina was found to be suitable as a scavenger for the removal of small quantities of HCl from gaseous streams. Stricter environmental demands and more precise operations in the chemical processing and petroleum refining industries however require more efficient HCl scavengers. It has now been found that these demands can be readily met by using as HCl scavenger bauxite or alumina subjected to thermal activation and promoted with an alkaline earth metal salt, for example, a calcium salt. The alkaline earth metal salt promoted aluminous material of the present invention exhibits a significantly higher HCl scavenging property than the prior art scavengers and simultaneously exhibits an increased stability in the presence of moisture under the scavenging conditions generally employed.